Photovoltaic Design and Installation Bucknell University Solar Scholars

Photovoltaic Design and Installation Bucknell University Solar Scholars Program Presenters: Barbara Summers ’ 11 Brian Chiu ‘ 11

Outline l l l Why Renewable Energy? The Science of Photovoltaics System Configurations Principle Design Elements Energy Efficiency The Solar Scholars program at Bucknell (walking tour)

What’s wrong with this picture? l l Pollution from burning fossil fuels leads to an increase in greenhouse gases, acid rain, and the degradation of public health. In 2005, the U. S. emitted 2, 513, 609 metric tons of carbon dioxide, 10, 340 metric tons of sulfur dioxide, and 3, 961 metric tons of nitrogen oxides from its power plants.

40% 85% of our energy consumption is from fossil fuels!

Why Sustainable Energy Matters l The world’s current energy system is built around fossil fuels – Problems: Fossil fuel reserves are ultimately finite l Two-thirds of the world' s proven oil reserves are locating in the Middle-East and North Africa (which can lead to political and economic instability) l

Why Sustainable Energy Matters l Detrimental environmental impacts – Extraction (mining operations) – Combustion l Global warming (could lead to significant changes in the world' s climate system, leading to a rise in sea level and disruption of agriculture and ecosystems)

Making the Change to Renewable Energy l l Solar Geothermal Wind Hydroelectric

Today’s Solar Picture Financial Incentives – – – Investment subsidies: cost of installation of a system is subsidized Net metering: the electricity utility buys PV electricity from the producer under a multiyear contract at a guaranteed rate Renewable Energy Certificates ("RECs")

Solar in Pennsylvania l l Pennsylvania is in fact a leader in renewable energy Incentives – – – Local & state grant and loan programs Tax credits & deductions REC’s (in 2006: varied from $5 to $90 per MWh, median about $20)

PA Alternative Energy Investment Fund l l $650 Million for Renewable Energy and Energy Efficiency The Pennsylvania Sunshine Program – provide $180 million in grants to Commonwealth homeowners and small businesses to purchase and install solar photovoltaic (PV) and solar hot water systems.

Deregulation and Grid Parity l l Current cost of electricity - 8. 58 cents/k. Wh 2010 PA electricity prices will be uncapped – l Est. 33+% increase projected by PPL The Solar America Initiative – goal of bringing solar to grid parity by 2015

Electricity

The Idea ≈

The Idea

The Idea

Terminology l Voltage – – – l Measured in Volts Electrical potential “Height” of water on one side of a dam compared to the other side Current – – – Measured in Amps Rate of electron flow “Speed” at which water flows through the dam

Terminology l Resistance – – The opposition of a material to the flow of an electrical current Depends on l l Material Cross sectional area Length Temperature

Types of Current l DC = Direct Current – – l PV panels produce DC Batteries store DC AC = Alternating Current – – – Utility power Most consumer appliances use AC Electric charge changes direction

Terminology l Watt – – – Measure of Power Rate of electrical energy Not to be confused with Current!

Typical Wattage Requirements Appliance Wattage Blender 350 TV (25 inch) 130 Washer 1450 Sunfrost Refrigerator (7 hours a day) refrigerator/freezer (13 hours a day) 112 Hair Dryer 1000 Microwave (. 5 sq-ft) Microwave (. 8 – 1 sq-ft) 750 1400 475

Terminology l Watt-hour (Wh) is a measure of energy – – l Unit quantity of electrical energy (consumption and production) Watts x hours = Watt-hours 1 Kilowatt-hour (k. Wh) = 1000 Wh

Symbols and Units Voltage: E or V (Volts) Current: I or A (Amps) Resistance: R or Ω (Ohms) Watt: W (Watt)

Grid-Tied System Overview

Harnessing the Sun

Grid-Tied System l Advantages – – l Easy to install (less components) Grid can supply power Disadvantages – No power if grid goes down

Solar Modules

Solar Domestic Hot Water

Solar Domestic Hot Water

Photovoltaic (PV) Hierarchy l Cell < Module < Panel < Array

Inside a PV Cell

Available Cell Technologies l Single-crystal or Mono-crystalline Silicon l Polycrystalline or Multi-crystalline Silicon l Thin film – Ex. Amorphous silicon or Cadmium Telluride

Monocrystalline Silicon Modules l l l Most efficient commercially available module (11% - 14%) Most expensive to produce Circular (square-round) cell creates wasted space on module

Polycrystalline Silicon Modules l l l Less expensive to make than single crystalline modules Cells slightly less efficient than a single crystalline (10% - 12%) Square shape cells fit into module efficiently using the entire space

Amorphous Thin Film l l l Most inexpensive technology to produce Metal grid replaced with transparent oxides Efficiency = 6 – 8 % Can be deposited on flexible substrates Less susceptible to shading problems Better performance in low light conditions that with crystalline modules

Selecting the Correct Module l Practical Criteria – – – Size Voltage Availability Warranty Mounting Characteristics Cost (per watt)

Current-Voltage (I-V) Curve

Effects of Temperature l As the PV cell temperature increases above 25º C, the module Vmp decreases by approximately 0. 5% per degree C

Effects of Shading/Low Insolation l As insolation decreases amperage decreases while voltage remains roughly constant

Shading on Modules Depends on orientation of internal module circuitry relative to the orientation of the shading. l SHADING can half or even completely eliminate the output of a solar array! l

Tools Insolation Pyranometer Surface Temperature Laser Thermometer

PV Wiring

Series Connections l Loads/sources wired in series – – VOLTAGES ARE ADDITIVE CURRENT IS EQUAL

Parallel Connections l Loads/sources wired in parallel: – – VOLTAGE REMAINS CONSTANT CURRENTS ARE ADDITIVE

Wiring Introduction l Should wire in Parallel or Series?

Wire Components l l l Conductor material = copper (most common) Insulation material = thermoplastic (most common) Wire exposed to sunlight must be classed as sunlight resistant

Color Coding of Wires l Electrical wire insulation is color coded to designate its function and use Alternating Current (AC) Wiring Direct Current (DC) Wiring Color Application Black Ungrounded Hot Red Positive White Grounded Conductor White Green or Bare Equipment Ground Red or any other color Ungrounded Hot (not NEC req. ) Negative or Grounded Conductor

Cables and Conduit l Cable: two or more insulated conductors having an overall covering l Conduit: metal or plastic pipe that contains wires

Wire Size l Wire size selection based on two criteria: – – Ampacity Voltage drop l Ampacity - Current carrying ability of a wire l Voltage drop: the loss of voltage due to a wire’s resistance and length

Safety Considerations l Unsafe Wiring – – – Splices outside the box Currents in grounding conductors Indoor rated cable used outdoors Single conductor cable exposed “Hot” fuses

Safety Equipment l Disconnects l Overcurrent Protection

Grounding l Provides a current path for surplus electricity to travel too (earth)

Solar Site & Mounting

Part 6: Learning Objectives l l l Understand azimuth and altitude Describe proper orientation and tilt angle for solar collection Describe the concept of “solar window” Evaluate structural considerations Pros and cons of different mounting techniques

Site Selection – Panel Direction l l Face true south Correct for magnetic declination

Altitude and Azimuth

Sun Chart for 40 degrees N Latitude

Solar Pathfinder l l An essential tool in finding a good site for solar energy is the Solar Pathfinder Provides daily, monthly, and yearly solar hours estimates

Site Selection – Tilt Angle Max performance is achieved when panels are perpendicular to the sun’s rays Year round tilt = latitude Winter + 15 lat. Summer – 15 lat.

Solar Access l Optimum Solar Window 9 am – 3 pm l Array should have NO SHADING in this window (or longer if possible)

General Considerations l Weather characteristics – – l Site characteristics – – l Wind intensity Estimated snowfall Corrosive salt water Animal interference Human factors – – – Vandalism Theft protection Aesthetics

General Considerations Continued l l Loads and time of use Distance from power conditioning equipment Accessibility for maintenance Zoning codes

Basic Mounting Options l Fixed – l l Roof, ground, pole Integrated Tracking – Pole (active & passive)

Pole Mount Considerations l Ask manufacturer for wind loading specification for your array – – – l Pole size Amount of concrete Etc. Array can be in close proximity to the house, but doesn’t require roof penetrations

Tracking Considerations l Can increase system performance by: – – l 15% in winter months 30% in summer months Adds additional costs to the array

Passive Vs. Active: – Linear actuator motors controlled by sensors follow the sun throughout the day

Passive Vs. Active Passive: – – Have no motors, controls, or gears Use the changing weight of a gaseous refrigerant within a sealed frame member to track the sun

Roof Mount Considerations l l l simple and cheap to install offer no flexibility in the orientation of your solar panel can only support small photovoltaic units.

Roof Mount Considerations l l Penetrate the roof as little as possible Weather proof all holes to prevent leaks – l l l May require the aid of a professional roofer Re-roof before putting modules up Leave 4 -6” airspace between roof and modules On sloped roofs, fasten mounts to rafters not decking

Building Integrated PV

Costs

Solar Energy System l l l $10, 000 -$15, 000 1 k. W system $16, 000 -$20, 000 2 k. W system $35, 000 -$45, 000 5 k. W system l About half the power for a conventional home

Solar Hot Water System l usually between $5, 000 to $6, 000

Solar Energy Incentives l Tax credits and deductions – l l 30% tax credit Local & state grant and loan programs PA Alternative Energy Investment Fund – Pennsylvania Sunshine Program l 35% rebate

Further Information on Incentives l www. sedacog. erc. org – l l SEDA COG www. desireusa. org www. solarpowerrock. com/pennsylvania

Energy Efficiency

Part 7: Learning Objectives l l l Identify cost effective electrical load reduction strategies List problematic loads for PV systems Describe penalties of PV system components Explain phantom loads Evaluate types of lighting; efficiency comparison

1. Conservation 2. Efficiency 3. Renewable Energy

Practical Efficiency Recommendations l l For every $1 spent on energy efficiency, you save $3 -$5 on system cost Start with your load use: – – Do it efficiently Do with less Do without Do it while the sun shines

Improving Energy Efficiency in the Home l Space Heating: – – – – Insulation Passive solar design Wood stoves Propane Solar hot water Radiant Floor/ baseboard Efficient windows l Domestic hot water heating – – – Solar thermal Propane/natural gas On demand hot water

Improving Energy Efficiency in the Home l Washing machines – Energy efficient front loading machine l Cooling – – – Ceiling fans Window shades Insulation Trees Reflective attic cover Attic fan

Phantom Loads

Phantom Loads l Cost the United States: – – l $3 Billion / year 10 power plants 18 million tons of CO 2 More pollution than 6 million cars TV’s and VCR’s alone cost the US $1 Billion/year in lost electricity

Lighting Efficiency l Factors effecting light efficiency – – Type of light Positioning of lights Fixture design Color of ceilings and walls

Incandescent Lamps l Advantages – – – Most common Least expensive Pleasing light l Disadvantages – – Low efficiency Short life ~ 750 hours Electricity is conducted through a filament which resists the flow of electricity, heats up, and glows Efficiency increases as lamp wattage increases FROM THE POWER PLANT TO YOUR HOME INCANDESCENT BULBS ARE LESS THAN 2% EFFICIENT

Fluorescent Bulbs l l l Less wattage, same amount of lumens Longer life (~10, 000 hours) May have difficulty starting in cold environments Not good for lights that are repeatedly turned on and off Contain a small amount of mercury

Light Emitting Diode (LED) Lights l Advantages – – Extremely efficient Long life (100, 000 hours) Rugged No radio frequency interference l Disadvantages – – Expensive (although prices are decreasing steadily) A relatively new technology

Ready for a field tour? l Questions? If you are interested in anything you have seen today and would like to get involved, please contact any member of the Solar Scholars team: Barbara Summers or Brian Chiu (bls [email protected] edu or bc [email protected] edu)

Solar Scholars Website http: //www. bucknell. edu/x 20303. xml

The END l Thank you for participating in this lecture series l Now lets go out into the field and take a look at the systems that we have already installed.

Batteries

Grid-Tied System l Advantages – – l Low: Easy to install (less components) Grid can supply power Disadvantages – No power when grid goes down

Part 4: Learning Objectives l l l Battery basics Battery functions Types of batteries Charging/discharging Depth of discharge Battery safety

Batteries in Series and Parallel l Series connections – l Builds voltage Parallel connections – Builds amp-hour capacity

Battery Basics The Terms: n Battery n A device that stores electrical energy (chemical energy to electrical energy and vice-versa) n Capacity n Amount of electrical energy the battery will contain n State of Charge (SOC) n Available battery capacity n Depth of Discharge (DOD) n Energy taken out of the battery n Efficiency n Energy out/Energy in (typically 80 -85%)

Functions of a Battery n n Storage for the night Storage during cloudy weather Portable power Surge for starting motors **Due to the expense and inherit inefficiencies of batteries it is recommended that they only be used when absolutely necessary (i. e. in remote locations or as battery backup for grid-tied applications if power failures are common/lengthy)

Batteries: The Details Types: n n Primary (single use) Secondary (recharged) Shallow Cycle (20% DOD) Deep Cycle (50 -80% DOD) Charging/Discharging: n n Unless lead-acid batteries are charged up to 100%, they will loose capacity over time Batteries should be equalized on a regular basis

Battery Capacity: n Amps x Hours = Amp-hours (Ah) 100 Amp-hours n n n = 100 amps for 1 hour 1 amp for 100 hours 20 amps for 5 hours Capacity changes with Discharge Rate The higher the discharge rate the lower the capacity and vice versa The higher the temperature the higher the percent of rated capacity

Rate of Charge or Discharge Rate = C/T C = Battery’s rated capacity (Amp-hours) T = The cycle time period (hours) Maximum recommend charge/discharge rate = C/3 to C/5

Battery Safety l Batteries are EXTREMELY DANGEROUS; handle with care! – Keep batteries out of living space, and vent battery box to the outside – Use a spill containment vessel – Don’t mix batteries (different types or old with new) – Always disconnect batteries, and make sure tools have insulated handles to prevent short circuiting

Grid-Tied System (With Batteries) l Complexity – l High: Due to the addition of batteries Grid Interaction – – Grid still supplements power When grid goes down batteries supply power to loads (aka battery backup)

Controllers & Inverters

Grid-Tied System l Advantages – – l Low: Easy to install (less components) Grid can supply power Disadvantages – No power when grid goes down

Part 5: Learning Objectives l l Controller basics Controller features Inverter basics Specifying an inverter

Controller Basics Function: l To protect batteries from being overcharged Features: l Maximum Power Point Tracking – Tracks the peak power point of the array (can improve power production by 20%)!!

Additional Controller Features l l Voltage Stepdown Controller: compensates for differing voltages between array and batteries (ex. 48 V array charging 12 V battery) – By using a higher voltage array, smaller wire can be used from the array to the batteries Temperature Compensation: adjusts the charging of batteries according to ambient temperature

Other Controller Considerations l l When specifying a controller you must consider: – DC input and output voltage – Input and output current – Any optional features you need Controller redundancy: On a stand-alone system it might be desirable to have more then one controller per array in the event of a failure

Inverter Basics Function: l An electronic device used to convert direct current (DC) electricity into alternating current (AC) electricity Drawbacks: l l l Efficiency penalty Complexity (read: a component which can fail) Cost!!

Specifying an Inverter l What type of system are you designing? – – l Stand-alone with back-up source (generator) Grid-Tied (without batteries) Grid-Tied (with battery back-up) Specifics: – – – – AC Output (watts) Input voltage (based on modules and wiring) Output voltage (120 V/240 V residential) Input current (based on modules and wiring) Surge Capacity Efficiency Weather protection Metering/programming